Stent with protruding branch portion for bifurcated vessels

ABSTRACT

The present invention is directed to a stent for use in a bifurcated body lumen having a main branch and a side branch. The stent comprises a radially expandable generally tubular stent body having proximal and distal opposing ends with a body wall having a surface extending therebetween. The surface has a geometrical configuration defining a first pattern, and the first pattern has first pattern struts and connectors arranged in a predetermined configuration. The stent also comprises a branch portion comprised of a second pattern, wherein the branch portion is at least partially detachable from the stent body.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of and claims the benefit ofU.S. application Ser. No. 11/145,223, filed Jun. 6, 2005, now U.S. Pat.No. 7,578,841, the entire contents of which is hereby incorporatedherein by reference. U.S. application Ser. No. 11/145,223 claims thebenefit of U.S. Provisional Application No. 60/577,579, filed Jun. 8,2004. U.S. application Ser. No. 11/145,223 is also acontinuation-in-part of U.S. patent application Ser. No. 10/644,550,filed Aug. 21, 2003, which claims the benefit of U.S. ProvisionalApplication No. 60/404,756, filed Aug. 21, 2002, U.S. ProvisionalApplication No. 60/487,226, filed Jul. 16, 2003, and U.S. ProvisionalApplication No. 60/488,006, filed Jul. 18, 2003. The entire contents ofthe above references are incorporated herein by reference.

U.S. application Ser. No. 11/145,223 is also a continuation-in-part ofU.S. patent application Ser. No. 10/683,165, filed Oct. 10, 2003, whichis a continuation of U.S. patent application Ser. No. 09/963,114, filedSep. 24, 2001, now U.S. Pat. No. 6,706,062, issued Mar. 16, 2004. Theentire contents of the above references are incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to the field of medical stents and, moreparticularly, to a stent for the treatment of lesions and other problemsin or near a vessel bifurcation.

BACKGROUND OF THE INVENTION

A stent is an endoprosthesis scaffold or other device that typically isintraluminally placed or implanted within a vein, artery, or othertubular body organ for treating an occlusion, stenosis, aneurysm,collapse, dissection, or weakened, diseased, or abnormally dilatedvessel or vessel wall, by expanding the vessel or by reinforcing thevessel wall. In particular, stents are quite commonly implanted into thecoronary, cardiac, pulmonary, neurovascular, peripheral vascular, renal,gastrointestinal and reproductive systems, and have been successfullyimplanted in the urinary tract, the bile duct, the esophagus, thetracheo-bronchial tree and the brain, to reinforce these body organs.Two important current widespread applications for stents are forimproving angioplasty results by preventing elastic recoil andremodeling of the vessel wall and for treating dissections in bloodvessel walls caused by balloon angioplasty of coronary arteries, as wellas peripheral arteries. Conventional stents have been used for treatingmore complex vascular problems, such as lesions at or near bifurcationpoints in the vascular system, where a secondary artery branches out ofa larger, main artery, with limited success rates.

Conventional stent technology is relatively well developed. Conventionalstent designs typically feature a straight tubular, single type cellularstructure, configuration, or pattern that is repetitive throughtranslation along the longitudinal axis. In many stent designs, therepeating structure, configuration, or pattern has strut and connectingmembers that impede blood flow at bifurcations. Furthermore, theconfiguration of struts and connecting members may obstruct the use ofpost-operative devices to treat a branch vessel in the region of avessel bifurcation. For example, deployment of a first stent in the mainlumen may prevent a physician from inserting a branch stent through theostium of a branch vessel of a vessel bifurcation in cases wheretreatment of the main vessel is suboptimal because of displaced diseasedtissue (for example, due to plaque shifting or “snow plowing”),occlusion, vessel spasm, dissection with or without intimal flaps,thrombosis, embolism, and/or other vascular diseases. As a result, thephysician may choose either to insert a stent into the branch in casesin which such additional treatment may otherwise be unnecessary, oralternatively the physician may elect not to treat, or to “sacrifice”,such side lumen. Accordingly, the use of regular stents to treatdiseased vessels at or near a vessel bifurcation may create a risk ofcompromising the benefit of stent usage to the patient after the initialprocedure and in future procedures on the main vessel, branch vessels,and/or the bifurcation point.

A regular stent is designed in view of conflicting considerations ofcoverage versus access. For example, to promote coverage, the cellstructure size of the stent may be minimized for optimally supporting avessel wall, thereby preventing or reducing tissue prolapse. The cellsize of a stent may be maximized for providing accessibility of bloodflow and of a potentially future implanted branch stent to branchvessels, thereby preventing “stent jailing”, and minimizing the amountof implanted material. Regular stent design has typically compromisedone consideration for the other in an attempt to address both. Problemsthe present inventors observed involving side branch jailing, fear ofplaque shifting, total occlusion, and difficulty of the procedure arecontinuing to drive the present inventors' into the development ofnovel, non-conventional or special stents, which are easier, safer, andmore reliable to use for treating the above-indicated variety ofvascular disorders.

Although conventional stents are routinely used in clinical procedures,clinical data shows that these stents are not capable of completelypreventing in-stent restenosis (ISR) or restenosis caused by intimalhyperplasia. In-stent restenosis is the reoccurrence of the narrowing orblockage of an artery in the area covered by the stent following stentimplantation. Patients treated with coronary stents can suffer fromin-stent restenosis.

Many pharmacological attempts have been made to reduce the amount ofrestenosis caused by intimal hyperplasia. Many of these attempts havedealt with the systemic delivery of drugs via oral or intravascularintroduction. However, success with the systemic approach has beenlimited.

Systemic delivery of drugs is inherently limited since it is difficultto achieve constant drug delivery to the inflicted region and sincesystemically administered drugs often cycle through concentration peaksand valleys, resulting in time periods of toxicity and ineffectiveness.Therefore, to be effective, anti-restenosis drugs should be delivered ina localized manner.

One approach for localized drug delivery utilizes stents as deliveryvehicles. For example, stents seeded with transfected endothelial cellsexpressing bacterial beta-galactosidase or human tissue-type plasminogenactivator were utilized as therapeutic protein delivery vehicles. See,e.g., Dichek, D. A. et al., “Seeding of Intravascular Stents WithGenetically Engineered Endothelial Cells”, Circulation, 80: 1347-1353(1989).

U.S. Pat. No. 5,679,400, International Patent Application WO 91/12779,entitled “Intraluminal Drug Eluting Prosthesis,” and InternationalPatent Application WO 90/13332, entitled “Stent With Sustained DrugDelivery” disclose stent devices capable of delivering antiplateletagents, anticoagulant agents, antimigratory agents, antimetabolicagents, and other anti-restenosis drugs.

U.S. Pat. Nos. 6,273,913, 6,383,215, 6,258,121, 6,231,600, 5,837,008,5,824,048, 5,679,400 and 5,609,629 teach stents coated with variouspharmaceutical agents such as rapamycin, 17-beta-estradiol, taxol anddexamethasone.

Although prior art references disclose numerous stent configurationscoated with one or more distinct anti-restenosis agents, they do notdisclose the inventive stent design of the present application. Thereis, therefore, a need for a stent design that can effectively provideostial branch support in a vessel bifurcation and effectively act as adelivery vehicle for drugs useful in preventing restenosis. This isparticularly true in complicated cases, such as lesions located at abifurcation.

SUMMARY OF THE INVENTION

The present invention is directed to a stent for use in a bifurcatedbody lumen having a main branch and a side branch. The stent comprises aradially expandable generally tubular stent body having proximal anddistal opposing ends with a body wall having a surface extendingtherebetween. The surface has a geometrical configuration defining afirst pattern, and the first pattern has first pattern struts andconnectors arranged in a predetermined configuration. The stent alsocomprises a branch portion comprised of a second pattern, wherein thebranch portion is at least partially detachable from the stent body.

In one embodiment, the second pattern is configured according to thefirst pattern having at least one absent connector, and in anotherembodiment, the second pattern has a plurality of absent connectors. Thesecond pattern may have second pattern struts, and the second patternstruts can be more densely packed than the first pattern struts.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, withreference to the accompanying drawings. With specific reference now tothe drawings in detail, it is stressed that the particulars shown are byway of example and for purposes of illustrative discussion of thepreferred embodiments of the present invention only, and are presentedto provide what is believed to be the most useful and readily understooddescription of the principles and conceptual aspects of the invention.In this regard, no attempt is made to show structural details of theinvention in more detail than is necessary for a fundamentalunderstanding of the invention, the description taken with the drawingsmaking apparent to those skilled in the art how the invention may beembodied in practice.

In the drawings:

FIG. 1 is an illustration of a blood vessel bifurcation having anobstruction;

FIGS. 2-4 are illustrations of prior art stents implemented at a bloodvessel bifurcation;

FIG. 5 is a flat view of an embodiment of an unexpanded stent inaccordance with the present invention;

FIG. 6 is an enlarged view of a portion of the unexpanded stent shown inFIG. 5;

FIG. 7 is a perspective view of the expandable branch portion of thestent of FIG. 5 in the expanded configuration;

FIG. 8 is an enlarged view of a portion of another embodiment of a stentaccording to the present invention;

FIG. 9 is an enlarged view of a portion of an alternative embodiment ofa stent according to the present invention;

FIG. 10 is a perspective view of the expandable branch portion of thestent of FIG. 9 in the expanded configuration;

FIG. 11 is a schematic view of the stent of FIG. 5 in the expanded stateimplemented at a blood vessel bifurcation;

FIG. 12 is a schematic view of the stent of FIG. 9 in the expanded stateimplemented at a blood vessel bifurcation;

FIG. 13 is an enlarged view of a portion of another embodiment of astent according to the present invention;

FIG. 14 is a flat view of another embodiment of an unexpanded stent inaccordance with the present invention;

FIG. 15 is an enlarged view of a portion of the unexpanded stent shownin FIG. 14;

FIG. 16 is a view of a portion of another embodiment of a stentaccording to the present invention;

FIG. 17 is a flat view of another embodiment of an unexpanded stent inaccordance with the present invention;

FIG. 18 is a perspective view of the expandable branch portion of thestent of FIG. 17 in the expanded configuration;

FIG. 19 is a flat view of another embodiment of an unexpanded stent inaccordance with the present invention;

FIG. 20 is an enlarged view of a portion of the stent of FIG. 19;

FIG. 21 is a view of the expandable branch portion of the stent of FIG.19 in the expanded configuration;

FIG. 22 is a flat view of another embodiment of an unexpanded stent inaccordance with the present invention;

FIG. 23 is a flat view of another embodiment of an unexpanded stent inaccordance with the present invention;

FIG. 24 is a view of an expandable branch portion of the stent of FIG.23 in the expanded condition;

FIGS. 25-28 are illustrations of the steps for a method of inserting astent of the present invention, according to one embodiment;

FIGS. 29-31 are illustrations of the steps for another method ofinserting a stent of the present invention;

FIG. 32 is a view of a herniated balloon for use with the method ofFIGS. 29-31;

FIG. 33 is a view of another stent delivery system for inserting a stentin accordance with another method of the present invention;

FIG. 34 is a flat view of another embodiment of an unexpanded stent inaccordance with the present invention;

FIG. 35 is a flat view of another embodiment of an unexpanded stent inaccordance with the present invention;

FIG. 36 is a flat view of another embodiment of an unexpanded stent inaccordance with the present invention;

FIG. 37 is a flat view of another embodiment of an unexpanded stent inaccordance with the present invention;

FIG. 38 is an enlarged view of a portion of the unexpanded stent shownin FIG. 37;

FIGS. 39-41 are illustrations of the steps for another method ofinserting a stent of the present invention;

FIG. 42 is an expanded view of the stent of FIG. 37 in the secondextended position;

FIG. 43 is a flat view of another embodiment of an unexpanded stent inaccordance with the present invention;

FIG. 44 is an enlarged view of a portion of the unexpanded stent shownin FIG. 43;

FIG. 45 is a flat view of another embodiment of an unexpanded stent inaccordance with the present invention;

FIG. 46 is an enlarged view of a portion of the unexpanded stent shownin FIG. 45;

FIG. 47 is a flat view of another embodiment of an unexpanded stent inaccordance with the present invention;

FIG. 48 is an enlarged view of a portion of the unexpanded stent shownin FIG. 47;

FIG. 49 is a flat view of another embodiment of an unexpanded stent inaccordance with the present invention;

FIG. 50 is an enlarged view of a portion of the unexpanded stent shownin FIG. 49;

FIG. 51 is a flat view of another embodiment of an unexpanded stent inaccordance with the present invention;

FIG. 52 is an enlarged view of a portion of the unexpanded stent shownin FIG. 51;

FIG. 53 is a flat view of another embodiment of an unexpanded stent inaccordance with the present invention;

FIG. 54 is an enlarged view of a portion of the unexpanded stent shownin FIG. 53;

FIG. 55 is a flat view of another embodiment of an unexpanded stent inaccordance with the present invention; and

FIG. 56 is an enlarged view of a portion of the unexpanded stent shownin FIG. 55.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to stents for placement at vesselbifurcations and are generally configured to at least partially cover aportion of a branch vessel as well as a main vessel. Referring to FIG.1, an exemplary blood vessel bifurcation 1 is shown, having a mainvessel 2 extending along a main vessel axis 3 and a branch vessel 4extending along a branch vessel axis 5. Main vessel 2 and branch vessel4 are disposed at an angle 11 of less than 90 degrees. An obstruction 6is located within bifurcation 1, spanning or at least partiallyobstructing main vessel 2 and a proximal portion branch vessel 4.

Prior attempts at relieving main vessel 2 and branch vessel 4 fromobstruction 6, such as the one depicted in FIG. 1, have beenproblematic. Referring to FIGS. 2-4, examples of prior methods andstructures for stenting an obstructed bifurcation are shown. As shown inFIG. 2, a first stent 8 is introduced into main vessel 2 and an accesshole or side opening in the wall of stent 8 is usually created with aballoon to provide access to branch vessel 4 and unobstructed blood flowthereto. Typically, the access hole is created by deforming the strutsand connectors of the main stent pattern, which may also deform the areaof the stent surrounding the created opening and lead to undesirableresults. Also, if stent 8 is used alone, at least a portion ofobstruction 6 located within branch vessel 4 is left without stentcoverage. Referring to FIGS. 3 and 4, one prior solution has been tointroduce a second stent 10 into branch vessel 4, for example via asecond catheter inserted through a side opening of first stent 8. As canbe seen in FIGS. 3 and 4, such a configuration may introduce additionalproblems. For example, as shown in FIG. 3, second stent 10 may notprovide full coverage of the portion of obstruction 6 in branch vessel 4due to the angle 11 of the side branch vessel 4 with respect to mainvessel 2 and the fact that the ends of the stent typically define aright angle to the longitudinal axis of the lumen. Alternatively, secondstent 10 may extend beyond the bifurcation into main vessel 2, as shownin FIG. 4, and cause potential obstruction of blood flow in main vessel2 and/or cause problems at the overlapping portions of stents 8 and 10.

Referring now to FIGS. 5-7, a stent 12 according to one embodiment ofthe present invention comprises stent body or wall 14 extending along alongitudinal axis 16 from a proximal end 20 to a distal end 22 anddefining a lumen 18 therein. Stent 12 may have a three-dimensionalgeometrical configuration having variable dimensions (length, width,height, depth, thickness, etc.). In a preferred embodiment, stent body14 is a generally tubular structure. As defined herein, “tubular” caninclude an elongate structure that has varied cross-sections and doesnot require that the cross-section be circular. For example, thecross-section of stent wall 14 may be generally oval. In an alternateembodiment, stent body 14 is generally cylindrical. Also, the stent body14 may have varied cross-sectional shapes along the longitudinal axis 16of the stent. For example, the circumferences in the proximal and distalparts of the stent may be different. This may occur, for example, ifduring stent delivery the delivery system causes the stent to distend.Lumen 18 represents the inner volumetric space bounded by stent body 14.In a preferred embodiment, stent 12 is radially expandable from anunexpanded state to an expanded state to allow the stent to expandradially and support the main vessel. In the unexpanded state, stentbody 14 defines a lumen 18 having a first volume, and in the expandedstate, stent body 14 defines a lumen 18 having a second volume largerthan the first volume.

FIG. 5 shows stent 12 in an unexpanded state in a flattened elevationalview. As shown in FIG. 5, stent body 14 has a generally cellularconfiguration and comprises a generally repeatable series of struts 24and connectors 26 configured in a predetermined general, overall, ormain pattern along the length of stent 12. Struts 24 comprise a pair oflongitudinal strut portions 25 joined by a curved portion 27 at theproximal ends. Struts 24 are interconnected by curved portion 29 at thedistal ends and formed into rings 28 that extend about the circumferenceof stent 12. A series of the circumferential rings 28 are spaced apartfrom one another longitudinally along the entire length of stent 12, andconnectors 26 connect rings 28 to each other longitudinally. Connectors26 extend generally longitudinally between adjacent Circumferentialrings 28 and connect to the respective curved portions 25, 29 oflongitudinally adjacent struts 24 of adjacent rings 28. In a preferredembodiment, connectors 26 are generally S-shaped or zigzag-shaped,although other patterns may also be used. Details of patterns that maybe used for stent 12 are described more fully in co-pending PCTapplication IL02/00840, filed Oct. 20, 2002, incorporated herein byreference in its entirety. Furthermore, many other strut and connectorpatterns may be used, and the present pattern is shown for illustrationpurposes only.

Stent 12 further includes a branch portion 30 located at some pointalong the length of stent 12. Branch portion 30 comprises a section orportion of stent wall 14 that is configured to extend into a branchvessel in a vessel bifurcation. In general, branch portion 30 isconfigured to be movable from an unextended position to an extendedposition. In the unextended position, branch portion 30 is disposed inthe volume defined by the unexpanded stent 12, that is, the branchportion 30 does not protrude radially from stent wall 14. In theextended position, the branch portion 30 extends outwardly from stentwall 14 and branch portion 30 is extended into the branch vessel. Asbest seen in FIG. 6, branch portion 30 comprises a stent wall section ofstent body 14 that is initially flush, coplanar, or cocylindrical withthe remainder of stent body 14 and may extend outwardly with respect tothe remainder of stent body 14. In this regard, branch portion 30 isgenerally adjacent an opening, slit, space, void, or other incongruityin the overall or main pattern of stent body 14. This configurationallows for access into a branch vessel, and at the same time allows forcircumferential alignment of the stent within the vessel prior todeployment. In other embodiments, multiple branch portions can beincorporated into the stent to permit multiple access to one or morevessels. In a preferred embodiment, branch portion 30 may be positionedin the midsection of stent 12. In alternate embodiments, branch portion30 may be positioned anywhere along the length of stent 12.

As best seen in FIG. 6, in a first embodiment, branch portion 30comprises a portion of branch ring 32 and is positioned adjacent andproximal to an opening 34. Upon extension of branch portion 30, theportion of branch ring 32 adjacent opening 34 extends into the branchvessel, whereas the circumferential ring 28 adjacent branch ring 32 doesnot extend into the branch vessel. Opening 34 is formed by an absence ofat least one connector 26 adjoining branch ring 32 with a branchopposing ring 33. In some embodiments, four adjacent connectors areabsent; however, in alternate embodiments any number of connectors maybe absent to create opening 34. In this embodiment, branch ring 32 issubstantially similar geometrically to circumferential rings 28 andcomprises branch ring struts 36 substantially similar to struts 24;however, a plurality of adjacent struts are free from connectors 26adjacent opening 34. In this regard, branch ring 32 is at leastpartially detachable from stent body 14 to facilitate at least a portionof branch ring 32 to extend outwardly with respect to stent body 14. Insome embodiments, the geometry of branch ring 32 may vary with respectto circumferential rings 28, and branch ring struts 36 may havedifferent configurations than struts 24.

When stent 12 is expanded, as shown in FIG. 7, branch portion 30 isextended into the branch vessel, causing a portion of branch ring 32 toat least partially cover the inner surface of the branch vessel 4. Thus,in a preferred embodiment, the stent coverage in the branch vesselincludes at least partial coverage of the proximal side of the innerbranch vessel wall.

Various alternative embodiments provide varying geometries of branchportion 30. For example, branch ring 32 may vary with respect tocircumferential rings 28, and branch ring struts 36 may have differentconfigurations than struts 24. In one alternate embodiment, branch ringstruts 36 are longer than struts 24. In another embodiment, branch ringstruts 36 are more closely packed circumferentially, resulting in agreater number of branch ring struts 36 per area within branch ring 32as compared to circumferential rings 28. In another embodiment, branchring struts 36 may be thinner than struts 24. In yet another embodiment,branch ring struts 36 may be made of a different material than struts24.

Referring to FIG. 8, another alternate embodiment of stent 19 is shownwherein a branch portion 30 comprises a branch ring 32 having branchring struts 36 that are longer than struts 24 and a greater number ofbranch ring struts 36 provided as compared to the number of struts 24 incircumferential rings 28, resulting in a more closely packed branch ring32. Furthermore, the number of branch ring connectors 38 on both sidesof branch ring 32 is lower per branch strut 36 than the number ofconnectors 26 per strut 24. Opening 34 is adjacent branch ring 32 on adistal side thereof, and the distal ends 46 of at least one, andpreferably a plurality, of branch ring struts 40, 42, 44 are free fromconnectors and detachable from stent body 14. In this embodiment, twobranch ring struts 48 and 50 positioned laterally adjacent struts 40,42, and 44 have proximal ends 52 free from connectors. In this regard,free proximal ends 52 provide less resistance to movement of branch ring32 during outward expansion with respect to stent body 14. This sameprocedure can be used to provide one, two, three or more proximal endsin the ring free of connectors. Additionally, the shape andconfiguration of branch ring connectors 38 is different than those ofconnectors 26. For example branch ring connectors along the proximalside of branch ring 32 are longer than connectors 26 to facilitategreater expansion of branch portion 30 into a vessel side branch. Also,branch ring connectors along the distal side of branch ring 32 areshaped and oriented differently than connectors 26 to facilitate greaterexpansion of branch portion 30 into the branch vessel. In alternateembodiments, branch ring connectors 38 may also differ among themselves.Also, the longer branch ring struts 36 are generally more flexible thancomparable shorter struts because the added length permits moredeflection. Also, the added length permits greater coverage vessel wallcoverage due to deeper penetration into the branch vessel duringextension. In alternate embodiments, different geometries andorientations of branch ring connectors 38 may be used.

Referring to FIG. 9, another alternate embodiment of stent 29 is shownhaving a branch portion 30 similar to that of the embodiment of FIG. 8,except branch ring struts 40, 42, and 44 are longer than the otherbranch ring struts 36, and the distal ends thereof define an arcuateprofile to the proximal side of opening 34. Also, central strut 42 islonger than struts 40, 44 adjacent to strut 42. In this regard, whenbranch portion 30 is extended, struts 40, 42, and 44 extend further intothe branch vessel and provide more coverage of the vessel wall than theembodiment depicted in FIG. 8. In this regard, this embodiment may morereadily cover an obstruction in a bifurcation vessel such as the onedepicted in FIG. 1 and, therefore, may provide better blood flow to abranch vessel. Furthermore, as described in more detail below, thisembodiment facilitates the use of a second stent in the branch vessel.

Referring to FIG. 10, stent 29 of FIG. 9 is shown in an expanded statewith branch portion 30 extended into the branch vessel, causing branchring 32 to at least partially cover the inner surface of the branchvessel on the proximal side. The distal end of strut 42 of branch ring32 extends further into the branch vessel than the distal ends of struts40, 44 because strut 42 is longer in this embodiment than adjacentstruts 40, 44. In this regard, a generally tapered, straight or linearprofile along the distal perimeter of branch portion 30 is created whenbranch portion 30 is expanded into the branch vessel.

Referring to FIGS. 11 and 12, schematic views are shown of stents 12, 29of FIGS. 5 and 9, respectively, in the expanded state as implemented ata blood vessel bifurcation. As shown in FIG. 11, stent 19 of theembodiment of FIG. 8 has a generally curved or radial profile along thedistal perimeter 45 of branch portion 30 as it extends into branchvessel 4. The generally curved or radial profile is due to theparticular geometry of branch portion 30 of stent 19 of the embodimentof FIG. 8. In particular, because all of the branch ring struts 36 ofbranch ring 32 are of equal length in this embodiment, the distal endsof struts 36 radially expand equidistantly into branch vessel 4, therebycreating a generally curved or radial profile along the distal perimeter45 of branch portion 30. Referring to FIG. 12, stent 29 of theembodiment of FIG. 9 has a generally tapered, straight or linear profilealong the distal perimeter 47 of the branch portion 30 of the stent asit extends into branch vessel 4. The generally straight or linearprofile in FIG. 12 is a result of the particular geometry of branchportion 30 of stent 29 of the embodiment of FIG. 9. In particular,because central strut 42 of branch ring 32 is longer in this embodimentthan struts 40, 44 adjacent to strut 42, the distal end of strut 42extends further into branch vessel 4 than the distal ends of struts 40,44, as best seen in FIG. 10, thus creating a generally tapered, straightor linear profile along the distal perimeter of branch portion 30. In apreferred embodiment, the linear profile is at a right angle withrespect to the axis of branch vessel 4. In alternative embodiments,however, the linear profile may be at any angle with respect to the axisof branch vessel 4. One advantageous feature of the linear profile alongthe distal perimeter of branch portion 30 shown in FIG. 12 is that if asecond stent 51 were to be used in branch vessel 4, the linear profilefacilitates better alignment with the second stent and permits coverageof a larger surface area of the branch vessel wall. For example, if asecond stent 51 were to be used in combination with stent 12 of FIG. 11,gaps may exist between the two stents at the interface between theradial distal perimeter 45 and an abutting straight or linear edge of asecond stent, whereas a close abutting interface may be achieved withstent 29 of FIG. 12.

Referring to FIG. 13, another embodiment of stent 39 is shown having analternative embodiment of a branch portion 30 similar to that of theembodiment of FIG. 9, except lateral branch ring struts 48 and 50 arelonger than the other branch ring struts 36, and the proximal ends 52 ofbranch ring struts 48, 50 extend proximally beyond the other branch ringstruts into a space between the branch ring 32 and the adjacentcircumferential ring 28. Branch ring struts 48, 50 have proximal ends 52free from connectors and provide less resistance to movement of branchring 32 during outward expansion with respect to stent body 14. In thisregard, the longer lateral branch ring struts 48, 50 function similar toa hinge and further facilitate extension of branch ring portion 30outwardly, which may accommodate a branch vessel disposed at a greaterangle 11 (FIG. 1) as compared to stent 29 of the embodiment of FIG. 9.Again, since struts 40, 42, and 44 are longer than branch ring struts36, they are more flexible and provide more coverage of a vessel wallthan the embodiment depicted in FIG. 8.

Referring now to FIGS. 14 and 15, another embodiment of stent 49 isshown having a stent body 14 that has a longitudinal section 53 that hasa different pattern than main pattern 54. Longitudinal section 53comprises a generally repeatable series of struts 56 and connectors 58that are smaller in dimension than struts 24 and connectors 26, but areformed into a similar geometrical pattern as main pattern 54. In thisregard, the struts 56 are more numerous per area within rings 28, andrings 28 are more numerous per area in section 53 because the length ofstruts 56 is shorter than the length of struts 24 and the length ofconnectors 58 is shorter than the length of connectors 26. In apreferred embodiment, the same number of connectors 58 extend betweenadjacent rings 28; however, because the struts are more numerous inlongitudinal section 53, connectors 58 extend longitudinally betweenevery other strut of adjacent rings 28. As shown in FIG. 15, stent 49further includes a branch portion 30 positioned within section 53.Branch portion 30 comprises a branch ring 32 adjacent an opening 34.Opening 34 is formed by an absence of at least one connector 26adjoining branch ring 32 with branch opposing ring 33. In a preferredembodiment, two adjacent connectors are absent; however, in alternateembodiments any number of connectors may be absent to create opening 34.In this embodiment, branch ring 32 is substantially similargeometrically to circumferential rings 28 and comprises branch ringstruts 36 substantially similar to struts 56; however, a plurality ofadjacent struts are free from a connectors 58 adjacent opening 34 andbranch ring 32 is at least partially detachable from stent body 14 atopening 34 to facilitate at least a portion of branch ring 32 to extendoutwardly with respect to stent body 14. The generally smaller strutsand connectors of longitudinal section 53 provide for freer movement ofthe strut and connector material and facilitate conformance to a vesselwall. The smaller struts and connectors also provide for a relativelymore dense surface area coverage of the branch vessel wall, which may beadvantageous in achieving a more uniform coverage around the ostium. Inparticular, this embodiment may provide particularly advantageouscoverage of a geometrically complex obstruction in a bifurcation vesselsince the relatively small pattern may flex or contour around theobstruction and provide coverage therefor. Also, this embodiment isadvantageous for relatively small obstructions as the smaller patternmay cover more surface area of obstruction.

Referring to FIG. 16, another embodiment of stent 59 is shown andincludes an alternate branch portion 30 comprising a portion of threeadjacent branch ring sections 60, 62, 64 connected and extendingcircumferentially from two adjacent circumferential rings 28. Branchring sections 60, 62, 64 each includes a plurality of branch struts 66and are connected in the longitudinal direction by branch connectors 68.Struts 66 are shorter longitudinally than struts 24 of rings 28 andconnectors 68 are smaller than connectors 26. The distal ring 60 isadjacent opening 34 and the distal ends of struts 66 of ring 60 aredetachable from stent body 14 at opening 34 to permit extension of atleast a portion of branch ring sections 60, 62, 64 to expand outwardlywith respect to stent body 14. In this embodiment, the three branch ringsections 60, 62, 64 may extend outwardly in a more radial fashion andthis branch portion 30 may be particularly advantageous for adapting orconforming to the shape of the proximal side of the ostium. Furthermore,the branch portion of this embodiment may more readily extend or flexaround an obstruction in a bifurcation vessel such as the one depictedin FIG. 1 while providing branch wall coverage and better blood flow tothe branch vessel.

Referring to FIGS. 17 and 18, an alternate embodiment of stent 69 isshown and includes an alternate branch portion 30. In this particularembodiment, branch portion 30 comprises support struts 70 and anexpandable ring 72. Branch portion 30 defines at least one side opening74. In one embodiment, the dimensions of the cell defining side opening74 are such that the side opening 74 (prior to expansion of the stent)is larger than other openings in stent body 14. The presence of sideopening 74 is generally configured to accommodate a side sheaththerethrough and allow a physician to access a branch vessel during orafter a procedure. In a particular embodiment, as shown in FIG. 17, sideopening 74 is surrounded by expandable ring 72 of continuous material.In alternative embodiments, expandable ring 72 comprises unattachedportions, or one portion that only partially covers side opening 74. Aseries of support struts 70 connect expandable ring 72 with struts 24and connectors 26. Support struts 70 preferably comprise patterns in afolded or wrap-around configuration that at least partially straightenout during expansion, allowing expandable ring 72 to protrude into thebranch vessel.

In this embodiment, when stent 69 is expanded, as shown in FIG. 18,branch portion 30 is extended into the branch vessel, causing expandablering 74 to at least partially cover the inner surface of the branchvessel. Thus, in a preferred embodiment, the stent coverage in a portionthe branch vessel includes the full circumference of the inner branchvessel wall. In alternative embodiments, partial coverage or severalsections of coverage are present.

Referring to FIGS. 19-21, another embodiment of a stent 79 is shownhaving a main stent body 14 and another embodiment of a branch portion30. FIGS. 19 and 20 show stent 79 in the unexpanded condition wherebranch portion 30 has not been deployed. FIG. 21 shows the stent 79 inthe expanded configuration where the branch portion 30 has beenexpanded. As shown, main stent body 14 includes a main stent patternhaving a generally repeatable ring 28 and connector 26 pattern. Branchportion 30 and the surrounding midsection 80 interrupt the repeatablering 28 and connector 26 pattern of stent 79. In this embodiment, branchportion 30 is configured to be both radially expandable andlongitudinally extendable into the branch vessel and relative to itslongitudinal axis 83 so that, in a preferred embodiment, the branchportion 30 contacts the entire periphery or circumference of the innerwall of the branch vessel in the expanded configuration. In this regard,branch portion 30 preferably provides 360° coverage of the wall of thebranch vessel. That is, branch portion 30 can be extended outward withrespect to longitudinal axis 81 of stent 79, and can also be expandedradially about axis 83 so as to contact the vessel (thereby allowing itto be adjustable with respect to vessel size).

Referring to FIG. 20, an enlarged view of section 80 of stent 79 isshown. In a preferred embodiment, a structural support member 84 may beprovided as a transition between the main stent body 14 and branchportion 30. In one aspect of a preferred embodiment, structural supportmember 84 may be elliptical to accommodate branch vessels extending atan angle to the main vessel. In alternate embodiment, other shapes ofsupport member 84 can be used to accommodate the vasculature. Thestructural support member 84 may include a continuous ring. In thisembodiment, structural support member 84 is a full, non-expandable ringand it does not expand radially beyond a particular circumference.

As shown in FIGS. 19 and 20, two concentric rings, inner ring 86 andouter ring 88, are positioned within structural support member 84 andsurround a generally circular central branch opening 34 to provideaccess to the side branch vessel when stent 79 is in the unexpandedcondition. Rings 86 and 88 are interconnected by a plurality of innerconnectors 90. Outer ring 88 is connected to structural support member84 by a plurality of outer connectors 92. Rings 86 and 88 are generallycurvilinear members. For example, rings 86, 88 can be defined byundulation petals, prongs, or peaks 94. In a preferred embodiment, eachring 86, 88 have the same number of undulation peaks 94, but the innerring may be more closely or tightly arranged, as shown. In anotherpreferred embodiment, each ring 86, 88 has eight pedals or undulationpeaks 94, although in alternate embodiments each ring can have anynumber of undulation peaks, and the number of peaks need not be equalfor each ring. The undulation peaks 94 generally include a pair of strutportions 96 interconnected by curved portions 98, and the strut portionsthemselves are connected to adjacent strut portions by another curvedportion. In a preferred embodiment, eight outer connectors 92 extendbetween structural support member 84 and outer ring 88, and each outerconnector 92 is attached at one end to approximately the middle of astrut portion 96 of outer ring 88 and the structural support member 84at the other end. As shown, outer connectors 92 may also have anundulated shape, although in alternate embodiments outer connectors 92may have differing shapes. In another aspect of the preferredembodiment, outer connectors 92 may be evenly or symmetrically spacedabout the structural support member 84. The inner ring 86 is attached tothe outer ring 88 by a plurality of inner connectors 90 and, in apreferred embodiment, eight inner connectors 90 connect the rings. Innerconnectors 90 extend from curved portion 98 of outer ring 88 to curvedportion of inner ring 86. As shown in FIG. 20, in a preferredembodiment, inner connectors 90 have a simple curved shape. Otherquantities, configurations, sizes and arrangements of connectors, ringsand spacing can be used depending upon the desired results. Varying theconnectors can provide for different amounts of flexibility andcoverage. The type of configuration of rings and connectors shownaddresses the need for radial and longitudinal expansion of branchportion 30, as well as branch vessel coverage. Other configurations andarrangements for the branch portion can be used in accordance with theinvention.

Referring again to FIGS. 19 and 20, the stent pattern surrounding branchportion 30 may be modified with a different pattern to accommodatebranch portion 30, as can all of the aforementioned embodiments. Inparticular, the rings 28 in the midsection 80 may be configured anddimensioned to be denser to provide sufficient coverage and flexibilityto compensate for the area occupied by branch portion 30.

Referring now to FIG. 21, stent 79 is shown in the expandedconfiguration, with branch portion 30 deployed. Upon expansion of branchportion 30, the inner and outer rings 86, 88 shift about thelongitudinal branch axis 83 and expand laterally away from the mainstent body 14 and into the branch vessel to form a branch coverageportion. Upon expansion, the outer connectors 92 can move outwardly andthe inner connectors 90 can straighten to a position substantiallyparallel to longitudinal branch axis 83. In a preferred embodiment, theexpanded rings 86, 88 have substantially the same expanded diameter,although in alternate embodiments rings 86, 88 could also have differentdiameters to accommodate a tapered vessel, if, for example a taperedballoon is used. The branch portion 30 can be extended at differentangles to the longitudinal axis 81 of the stent depending upon thegeometry of the branch vessel being treated. In this embodiment, thebranch portion 30 may preferably extend into the branch vessel about1.5-3 mm.

Referring now to FIG. 22, another embodiment of a stent 89 is shownhaving a main stent body 14 and another embodiment of a branch portion30. Stent 89 is substantially similar to stent 79, except stent 89 has adiscontinuous support member 104 surrounding a two concentric ring 86,88 structure. Support member 104 has a generally elliptical shape andincludes a plurality of discontinuities 106 along the perimeter. Theconfiguration of the discontinuous support member facilitates additionalflexibility of the branch portion during expansion and generallyprovides for accommodating a greater range of branch vessel geometries.In one aspect of a preferred embodiment, structural support member 84may be elliptical to accommodate branch vessels extending at an angle tothe main vessel.

Referring to FIGS. 23 and 24, another embodiment of a stent 99 is shownin the unexpanded and expanded states, respectively. Stent 99 comprisesa main stent body 14 and another embodiment of a branch portion 30.Stent 99 is substantially similar to stent 79, except stent 99 has abranch portion 30 including a support member 108 surrounding threeconcentric rings 110, 112, 114 instead of two. As can be seen in FIG.24, when stent 99 is expanded the three concentric ring structure ofthis embodiment facilitates additional branch wall support because agenerally more dense pattern is created in branch portion 30 with theaddition of another concentric ring.

Referring to FIG. 34, an alternate embodiment of a stent 220 is shownhaving a main stent body 14 and another embodiment of branch portion 30.FIG. 34 is a flat view of stent 220 shown in an unexpanded conditionwhere branch 30 has not been deployed. Main stent body 14 includes amain stent pattern having a generally repeatable ring 28 and connector26 pattern. Branch portion 30 and the surrounding midsection 80interrupt the repeatable ring 28 and connector pattern of stent 220.Branch portion 30 is configured to be extendable into the branch vesselsuch that the branch portion 30 contacts the entire periphery orcircumference of the inner wall of the branch vessel in the expandedconfiguration.

In a preferred embodiment, structural support members 224 may beprovided as a transition between the main stent body 14 and branchportion 30. Support members 224 comprise generally elliptical halfportions positioned in an opposing relation with a space 246therebetween. Support members 224 surround a two concentric ring 228,230 structure and a central branch opening 232. Branch opening 232provides access to the side branch vessel when stent 220 is in theunexpanded condition and a side sheath may pass through opening 232.Rings 228 and 230 are interconnected by a plurality of inner connectors234. Outer ring 230 is connected to structural support members 224 by aplurality of outer connectors 236. Rings 228, 230 are generallycurvilinear members and include undulation petals, prongs, or peaks 238.In this embodiment outer ring 230 includes a greater number of peaksthan inner ring 228. Preferably eight outer connectors and eight innerconnectors interconnect support members 224 and rings 228, 230. In thisembodiment, inner and outer connectors 234, 236 are generally straightmembers and are preferably aligned radially to extend toward the centerof branch portion 30. In operation, the intersection of outer connectors236 with support members 224 form a pivot point about which petals 238may unfold or pivot outward into the side branch vessel. In a preferredembodiment, the generally straight inner and outer connectors pivottogether such that the petals 238 open like a flower.

Referring to FIG. 35, an alternative embodiments of a stent 240 is shownhaving an alternate embodiment of a branch portion 30. Stent 240includes structural support members 244 as a transition between the mainstent body 14 and branch portion 30. Support members 244 comprisegenerally elliptical half portions positioned in an opposing relationwith a space 246 therebetween. Support members 244 surround a twoconcentric ring 248, 250 structure and a central branch opening 252.Rings 248 and 250 are interconnected by a plurality of inner connectors254. Outer ring 248 is connected to structural support members 244 by aplurality of outer connectors 256. Rings 248, 250 are generallycurvilinear members and include undulation petals, prongs, or peaks 258.An auxiliary access opening 255 interrupts rings 248, 250 and providesaccess to the side branch vessel when stent 240 is in the unexpandedcondition. A ring portion 257 extends between outer connectors 256proximal to auxiliary access opening 255. In this embodiment, auxiliaryaccess opening 255 is generally larger than central branch opening 252to more readily receive a side sheath therethrough and to allow forgreater access to the side branch. Auxiliary access opening 255 ispreferably positioned proximal to central branch opening 252 when loadedon a stent delivery system, however auxiliary access opening 255 canhave varying positions in alternate embodiments An alternate embodimentof a stent 260 is shown in FIG. 36 that is similar to stent 240 and itadditionally includes lateral connecting members 262 that extend throughspace 246 and connect the outer ring 250 to struts 264 laterally outsidebranch portion 30. In this regard, when branch portion 30 is extendedinto the side branch, struts 264 are pulled radially inward to supportthe circumference of the ostium. This additional structure improvesradial strength and provides additional support to the vessel wall.

In all of the above embodiments, the branch portion 30 protrudes intothe branch vessel when the stent is fully expanded. The branch portionupon expansion can extend into the branch vessel in different lengthsdepending upon the application. The amount of extension may vary in arange between about 0.1-10.0 mm. In one preferred embodiment, the lengthof extension is 1-3 mm. In another preferred embodiment, the length ofextension is approximately 2 mm. In alternative embodiments, the amountof extension into the branch vessel may be variable for differentcircumferential segments of branch portion 30. As shown in each of theembodiments, the branch portion is approximately 2.5 mm in width andabout 2.5-3.0 mm in length. However, the branch portion can bedimensioned to accommodate varying size branch vessels. The branchportion can be formed of any tubular shape to accommodate the branchvessel, including, oval or circular, for example.

In general, a wide variety of delivery systems and deployment methodsmay be used with the aforementioned stent embodiments. For example, acatheter system may be used for insertion and the stent may be balloonexpandable or self-expandable, or the stent may be balloon expandableand the branch portion self-expandable, or vice versa. Once the stent isin position in the main vessel and the branch portion is aligned withthe side branch the stent can be expanded. If the stent is balloonexpandable, the stent may be expanded with a single expansion ormultiple expansions. In particular, the stent can be deployed on a stentdelivery system having a balloon catheter and side sheath as described,for example, in U.S. Pat. Nos. 6,325,826 and 6,210,429, the entirecontents of which are incorporated herein by reference. In one preferredembodiment, a kissing balloon technique may be used, whereby one balloonis configured to expand the stent and the other balloon is configured toextend branch portion 30. After the main portion of the stent isexpanded in the main vessel, the stent delivery system may be removedand a second balloon may be passed through the side hole in the branchportion and expanded to expand the branch portion of the stent. In analternate embodiment, the same balloon may be inserted in the mainvessel inflated, deflated, retracted and inserted into the branchvessel, and then reinflated to expand branch portion 30 and cause it toprotrude into the branch vessel. Alternatively, the stent can bedelivered on two balloons and the main portion and the branch portioncan be expanded simultaneously. As needed, the branch portion can befurther expanded with another balloon or balloons. Yet anotheralternative is to use a specially shaped balloon that is capable ofexpanding the main and branch portions simultaneously. The stent canalso be deployed with other types of stent delivery systems.Alternatively, the stent, or portions of the stent, can be made of aself-expanding material, and expansion may be accomplished by usingself-expanding materials for the stent or at least branch portion 30thereof, such as Nitinol, Cobalt Chromium, or by using other memoryalloys as are well known in the prior art.

The construction and operation of catheters suitable for the purpose ofthe present invention are further described in U.S. patent applicationSer. No. 09/663,111, filed Sep. 15, 2000, which is acontinuation-in-part of U.S. patent application Ser. No. 09/614,472,filed Jul. 11, 2000, which is a continuation-in-part of U.S. patentapplication Ser. No. 09/325,996, filed Jun. 4, 1999, and 09/455,299,filed Dec. 6, 1999, the disclosures of all of which are incorporatedherein by reference. It should be noted that the catheters taught in theabove applications are exemplary, and that other catheters that aresuitable with the stents of the subject application are included withinthe scope of the present application. In alternative embodiments,catheters without balloons may be used. For example, if the stent iscomprised of memory alloy such as Nitinol or Cobalt Chromium, or is amechanically self-expanding stent, balloons are not necessarily includedon the catheters. Furthermore, any other catheter, including ones thatare not disclosed herein, may be used to position stents according tothe present invention.

Referring now to FIGS. 25-28, illustrations of the steps of one exampleof a method for employing a stent according to the invention are shown.By way of example, the method is depicted utilizing stent 12. Methodsfor positioning such a catheter system within a vessel and positioningsuch a system at or near a bifurcation are described more fully inco-pending U.S. patent application Ser. No. 10/320,719 filed on Dec. 17,2002, which is incorporated herein by reference in its entirety. Asshown in FIG. 25, a catheter system 120 is positioned proximal to abifurcation, using any known method. A branch guidewire 122 is thenadvanced through an opening in the stent and into the branch vessel 4,as shown in FIG. 26. In a preferred embodiment, the opening may be adesignated side branch opening, such as an opening formed by the absenceof some connectors 26, as described above. Branch portion 30 is adjacentthe opening. As shown in FIG. 27, if the side sheath 124 is attached tothe main catheter 120, the main catheter 120 is advanced along with theside catheter 124. Alternatively, if the side sheath 124 is separatefrom to the main catheter 120, the second catheter or side sheath 124 isthen advanced independently through the opening in the stent and intothe branch vessel. Branch portion 30 is positioned over a portion of thelumen of the branch vessel 4 as the side sheath 124 is inserted intobranch vessel 4. Referring to FIG. 28, a first balloon 126 located onmain catheter 120 is then expanded, causing expansion of the stent body,and a second balloon 128 located on the second catheter or side sheath124 is also expanded, causing branch portion 30 to be pushed outwardwith respect to the stent body, thus providing stent coverage of atleast a portion of the branch vessel. The balloons are then deflated andthe catheter system and guidewires are then removed.

Referring now to FIGS. 29-31, illustrations of the steps of anothermethod for employing a stent of the present invention is shown. By wayof example, the method is depicted utilizing stent 12. The depictedmethod may be accomplished using a catheter system having a maincatheter 131 including a herniated balloon 135 (FIG. 32). In particular,the stent can be deployed on a stent delivery system having a herniatedballoon as described, for example, in U.S. Patent Application No.60/488,006, filed Jul. 18, 2003, the entire contents of which areincorporated herein by reference. As shown in FIG. 29, the catheter 131includes a balloon 135 that has a protruding portion 137 that protrudesoutwardly from the cylindrical outer surface 134 of the balloon.

Referring to FIG. 32, the herniated balloon 135, shown in an expandedstate, has a generally cylindrical shape and the protruding portion 137can be any appendage or integral portion of the balloon that movesoutwardly from the outer surface 134 of the balloon upon inflation, inaccordance with the principles of the invention. In a preferredembodiment, the protruding portion 137 is a portion of the balloon wallthat has greater expandability than other portions of the balloon wallthat retain a generally cylindrical shape. In another embodiment,protruding portion 137 may be a solid structure attached to the balloonwall. The protruding portion 137 can have any shape desirable to effectdeployment of branch portion 30. In one preferred embodiment, protrudingportion 137 has a hemispherical shape. In another preferred embodiment,protruding portion 137 has an ovoid shape. In use, the stent 12 iscrimped onto the balloon 135 so that the protruding portion 137 ispositioned at the branch portion. As shown, the protruding portion 137is positioned adjacent or alongside the radially inward side of branchportion 30. The herniated balloon 135 is used to expand the branchportion 30 and/or deploy the outwardly deployable structure of stent 12by applying a force in the laterally outward direction to the expandableelements by deflecting these elements toward the side branch 4. Theprotruding portion 137 may be located at any position along the lengthof the balloon. For example, it can be located on the middle ⅓ of thestent.

In one embodiment, the balloon may be constructed of compositematerials. For example, a combination of elastomeric and semi to noncompliant materials such as urethane, silicone, and latex, (Elastomeric)polyethylene hytrel pebax polyarylethertherketone, polyoxymethylene,polyamide, polyester thermoplastic polyetheretherketone andpolypropylene (semi to non compliant), may be used. The balloon may alsobe constructed by combining the above-mentioned materials with woventextiles such as Kevlar, silk cotton, wool, etc. In this construction, atextile is wound or woven onto a rod that has the shape of the desiredherniated balloon and the polymer is then extruded or dip coated overthe rod. The composite is cured, heat set or adhesively fused together.The rod is then removed and the remaining shape is a herniated balloon.The balloon can also be constructed by adding an appendage to aconventional balloon by using a molded collar or adhesively attaching anobject to the surface of the balloon or by using a mound of adhesive tocreate the herniation or protruding portion. In an alternate embodiment,the balloon can be constructed by molding three small balloons andattaching them in tandem with the center balloon being round in shape.The balloon would share a common inflation port. When the balloon isinflated the center balloon becomes the herniation.

Referring again to FIGS. 29-31, protruding portion 137 may be configuredto fit directly into an opening in the stent. As shown in FIG. 29,catheter 131 is advanced over a guidewire 133 and positioned proximal tothe bifurcation. As shown in FIG. 30, the catheter is advanced until theprotruding portion 137 of the balloon is positioned at the bifurcation.In one embodiment, protruding portion 137 protrudes outwardly fromcatheter 131 enough so that it actually comes into contact with thebifurcation, thus providing a method of alignment with the branch vessel4. Finally, as shown in FIG. 31, balloon 135 is expanded, whichsimultaneously causes the stent to expand and branch portion 30 to bepushed toward the branch vessel 4. Upon inflation of the balloon, theherniated portion 137 expands and extends through the branch portion 30toward the side branch to open the entrance of the occluded side branchartery.

In an alternative method, the stent can be delivered using a herniatedballoon and a dual lumen delivery system. This system can include a maincatheter defining a first lumen with concentric guidewire lumen andballoon inflation lumen, a herniated balloon, as described above, on themain catheter, a side sheath with a guidewire lumen, and a stent. Thestent is crimped over the main catheter, balloon and side sheath withthe side sheath exiting the stent through a branch opening or side hole.The distal end of the side sheath is used for aligning the stent branchopening with the branch vessel 4.

In another embodiment, the appendage or herniation may be located on asecond catheter or side sheath of the delivery system, such as thesystem 138 depicted in FIG. 33. In this case, the system is atwo-balloon system. The smaller balloon 140 can be positioned in thestent in a similar manner as the herniation. The appendage or herniationmay have an inflation lumen 141 and a lumen for receiving a guidewire142 for locating the branch vessel 4.

Referring to FIGS. 37-38, a stent 312 according to another embodiment ofthe present invention comprises stent body or wall 314 extending along alongitudinal axis 316 from a proximal end 320 to a distal end 322 stentwall 314 has an exterior surface and an inner surface or undersurfacedefining a lumen 318 therein. Stent 312 is radially expandable from anunexpanded state to an expanded state to allow the stent to expandradially and support the main vessel. In the unexpanded state, stentbody 314 defines a lumen 318 having a first volume, and in the expandedstate, stent body 314 defines a lumen 318 having a second volume largerthan the first volume.

FIG. 37 shows stent 312 in an unexpanded state in a flattenedelevational view. As shown in FIG. 37, stent body 314 has a generallyrepeatable series of struts 324 and connectors 326 configured in apredetermined main pattern along the length of stent 312. As describedin previous embodiments, struts 324 comprise a pair of longitudinalstrut portions 325 joined by a curved portion 327 at the proximal ends.Struts 324 are interconnected by curved portion 329 at the distal endsand formed into rings 328 that extend about the circumference of stent312. A series of the circumferential rings 328 are spaced longitudinallyalong the entire length of stent 312, and connectors 326 connect rings328 to each other longitudinally. Connectors 326 extend generallylongitudinally between adjacent circumferential rings 328 and connect tothe respective curved portions 327, 329 of longitudinally adjacentstruts 324 of adjacent rings 328.

Stent 312 further includes a branch portion 330 located at some pointalong the length of stent 312. As described in previous embodiments,branch portion 330 comprises a section or portion of stent wall 314 thatis configured to extend into the ostium of a branch vessel in a vesselbifurcation. In general, branch portion 330 is configured to be movablefrom an unextended position to an extended position. In the unextendedposition, branch portion 330 is disposed in the volume defined by theunexpanded stent 312, that is, the branch portion 330 does not protruderadially from stent wall 314. In the extended position, the branchportion 330 extends outwardly from stent wall 314 and branch portion 330is extended into the branch vessel. As best seen in FIG. 38, branchportion 330 comprises a stent wall section of stent body 314 that isinitially flush, coplanar, or cocylindrical with the remainder of stentbody 314 and may extend outwardly with respect to the remainder of stentbody 314.

As best seen in FIG. 38, one embodiment of branch portion 330 comprisesa proximal branch portion 332 that is connected to a portion of branchring 334 and includes a distal branch portion 336 that extends into anopening 337 in the distally adjacent circumferential ring 338. In thisembodiment, distal branch portion 336 is not attached to ring 338;however in alternate embodiments distal branch portion may be attachedto ring 338. Upon extension of branch portion 330, the proximal branchportion 332 and distal branch portion 336 extend into the branch vessel,whereas the branch ring 334 and distally adjacent circumferential ring338 do not extend into the branch vessel. In this embodiment, branchportion 330 has a modified strut structure comprising a generally openstrut configuration with a row of distal branch portion struts 340, 342,344 in phase with and offset, or spaced, in the distal direction fromproximal branch portion struts 350, 352, 354. In this embodiment, therow of distal branch struts have a generally “W” configuration and thebranch struts have respective curved portions 341, 343, 345 at thedistal end interconnecting the longitudinal portions, e.g., 347, ofdistal branch portion struts 340, 342, 344. Distal branch struts 340,342, 344 are interconnected at the proximal end by curved portions 349,351. The outside lateral distal struts 340, 344 are connected to thecurved distal regions 360, 362 of outside lateral proximal struts 350,354, thus defining a single bounded space or opening 364 between thedistal branch portion struts 340, 342, 344 and the proximal branchportion struts 350, 352, 354. In alternative embodiments, branch portion330 may have varied geometries and configurations of proximal branchportion 332 and/or distal branch portion 336. For example, in alternateembodiments, the number of struts in the distal branch portion maydiffer from the number of struts in the proximal branch portion. Also,the size and shape of the proximal branch struts and distal branchstruts may be varied in alternate designs.

Referring now to FIGS. 39-42, illustrations of the steps of oneexemplary method for delivering stent 312 are shown. As shown in FIG.39, a catheter system 370 is positioned over a main guidewire 371proximal to a bifurcation, using any known method and branch portion 330is positioned adjacent the opening of branch vessel 4. A side sheath orbranch guidewire 372 is then advanced through opening 364 and into thebranch vessel 4, as shown in FIG. 40. As shown in FIG. 41, the secondcatheter or side sheath 372 is then advanced through opening 364 andinto the branch vessel. Branch portion 330 is positioned over a portionof the lumen of the branch vessel 4 as the side sheath 372 is insertedinto branch vessel 4. Stent 312 is then expanded, causing expansion ofthe stent body and causing branch portion 330 to extend outward withrespect to the stent body to a first extended position. In a preferredembodiment, a balloon 376 located on main catheter 370 may be used toexpand the stent. In one embodiment, balloon 376 may be a herniatedballoon or a combination of cylindrical and dimple balloons with anexpandable protrusion 374 positioned adjacent the branch portion 330.Upon expansion of stent 312, branch portion 330, including distal branchportion struts 340, 342, 344 and proximal branch portion struts 350,352, 354, may pivot at curved regions 364, 366, such that the distal endof branch portion 330 may extend outward from the remainder of stentbody 314 and into the branch vessel. When the branch portion 330 is inthe first extended position, stent coverage is provided to at least aportion of the branch vessel. In particular, a portion of branch portion330 at least partially covers the inner surface of the branch vessel,for example the proximal side of the branch vessel wall. Next, theballoon may be deflated and branch portion 330 may be further extendedto a second extended position, shown in FIG. 42. In particular, thebranch portion 330 may be extended into the second extended position bypivoting distal branch portion struts 340, 342, 344 inward about curvedregions 360, 362 and pivoting the proximal curved portions 349, 351downward about the outside lateral distal curved portions 341 and 345.As best seen in the fully expanded view of FIG. 42, in this secondextended position, distal branch portion struts 340, 342, 344 are spacedfrom the proximal branch portion struts 350, 352, 354 to support thebranch vessel wall opposite the proximal branch portion struts. It willbe recognized that the exterior surface of the proximal branch portionstruts 350, 352, 354 contact and support the branch vessel wall and theundersurface of the distal branch portion struts 340, 342, 344 contactand support the branch vessel opposite the proximal branch portionstruts in the second extended position. In this regard, the entireperiphery of the branch vessel wall may be provided with stent coverageas the proximal branch portion struts preferably cover and support aproximal portion of the branch vessel wall and the distal branch portionstruts preferably cover and support a distal portion of the branchvessel wall. Once branch portion 330 is extended to the second extendedposition the catheter system and guidewires are then removed.

Referring to FIGS. 43-44, an alternative stent 412 and branch portion430 is shown. Upon extension of branch portion 430, the proximal branchportion 432 and distal branch portion 436 extend into the branch vessel,whereas the branch ring 434 and distally adjacent circumferential ring438 do not extend into the branch vessel. In this embodiment, branchportion 430 is similar geometrically to branch portion 330 describedabove; however, distal branch portion 436 is attached to distallyadjacent ring 438 by a single connector 470. Connector 470longitudinally connects at least one of distal branch struts 440, 442,444 to ring 438. In this embodiment, connector 470 connects ring 438 toone of the proximal curved portions 449, 451 interconnecting distalbranch struts 440, 442, 444. In operation, branch portion 430 isextended in much the same manner as branch portion 330, except a portionof the distal branch portion adjacent connector 470 at least partiallyresists extension outward to the first extended position and the distalbranch portion may rotate outward with respect to the junction or pointat which connector 470 meets the branch struts. In the second extendedposition, connector 470 preferably contacts and supports a portion ofthe ostium or the transition area of the vessel wall where the mainvessel meets the branch vessel.

Referring to FIGS. 45-46, an alternative stent 512 and branch portion530 is shown. Upon extension of branch portion 530 outwardly from stentbody 514, the proximal branch portion 532 and distal branch portion 536extend into the branch vessel, whereas the branch ring 534 and distallyadjacent circumferential ring 538 do not extend into the branch vessel.In this embodiment, branch portion 530 is similar geometrically tobranch portion 430 described above; however, distal branch portion 536is attached to distally adjacent circumferential ring 538 by a pair ofconnectors 570, 572. Connectors 570, 572 each longitudinally connect atleast one of distal branch struts 540, 542, 554 to circumferential ring538. In this embodiment, connectors 570, 572 connect ring 538 to theproximal curved portions 549, 551 interconnecting distal branch struts540, 542, 544. In operation, branch portion 530 is extended in much thesame manner as branch portion 430, except a portion of the distal branchportion adjacent both connectors 570, 572 at least partially resistsextension outward to the first extended position and the distal branchportion may rotate outward with respect to the junction or point atwhich connectors 570, 572 meet the branch struts. In the second extendedposition, connectors 570, 572 preferably contact and support a portionof the ostium or the transition area of the vessel wall where the mainvessel meets the branch vessel.

Referring to FIGS. 47-48, an alternative stent 612 and branch portion630 is shown. In this embodiment, branch portion 630 is similargeometrically to branch portion 330 described above; however, proximalbranch portion 632 and distal branch portion 636 only have two branchstruts respectively. In this embodiment, branch portion 630 has amodified strut structure comprising a generally open strut configurationwith a row of distal struts 640, 642 in phase with and offset, orspaced, in the distal direction from proximal struts 650, 652. In thisembodiment, the row of distal branch struts 640, 642 have a similarsize, shape and configuration as proximal branch struts 650, 652. Distalbranch struts 640, 642 are interconnected at the proximal end by curvedportion 649. The outside lateral portions of distal struts 640, 642 areconnected to the curved proximal regions 660, 662 of outside lateralportions of proximal struts 650, 652, thus defining a single boundedspace or opening 664 between the distal branch portion struts 640, 642and the proximal branch portion struts 650, 652. In operation and uponexpansion of branch portion 630, distal branch portion struts 640, 642and proximal branch portion struts 650, 652 may pivot at curved regions660, 662, such that the distal end of branch portion 630 may extendoutward from the remainder of stent body 614 and into the branch vessel.When the branch portion 630 is in the first extended position, stentcoverage is provided to at least a portion of the branch vessel. Thebranch portion 630 may be extended into the second extended position bypivoting distal branch portion struts 640, 642 inward about curvedregions 660, 662 and pivoting the proximal curved portion 649 downwardabout the distal curved portions 641 and 645. In this second extendedposition branch portion struts 640, 642 are spaced from the proximalbranch portion struts 650, 652 to support the branch vessel wallopposite the proximal branch portion struts.

Referring to FIGS. 49-50, an alternative stent 712 and branch portion730 is shown. In this embodiment, branch portion 730 is similargeometrically to branch portion 330 described above; however the outsidelateral proximal branch struts 750, 754, extend proximally beyond theother branch ring struts and connect to adjacent struts at curvedregions 766, 768, positioned between the branch ring 734 and theproximally adjacent circumferential ring 728. In this regard, the longerlateral proximal branch struts 750, 754 function similar to a hinge andfurther facilitate extension of branch portion 730 outwardly. Asdescribed above with respect to other embodiments, in operation, branchportion 730 is configured to extend outwardly with respect to stent body714. When branch portion 730 is fully extended it may provide at leastpartial stent coverage of both the proximal and distal side of the innerbranch vessel wall. In particular, branch portion 730 may pivot atcurved regions 766, 768, such that the branch portion 730 is in a firstposition extended outward from the remainder of stent body 714 and intothe branch vessel to support a portion of the branch vessel wall. Branchportion 730 may be further extended to a second position by pivotingdistal branch portion struts 740, 742, 744 inward about curved regions760, 762 and pivoting the proximal curved portions 749, 751 downwardabout the outside lateral distal curved portions 741 and 745. In thissecond extended position, branch portion struts 740, 742, 744 are spacedfrom the proximal branch portion struts 750, 752, 754 to support thebranch vessel wall opposite the proximal branch portion struts. It willbe recognized that the exterior surface of the proximal branch portionstruts 750, 752, 754 contact and support the branch vessel wall and theundersurface of the distal branch portion struts 740, 742, 744 contactand support the branch vessel wall in the second extended position.Stent 712 may be delivered in a similar manner as described above withrespect to stent 312 and branch portion 730 may be extended in a similarmanner as branch portion 330. In particular, branch portion be movedfrom the first extended position to the second extended position byapplying force in the distal direction on a second catheter extendingthrough opening 764 to move and/or pivot the distal portion struts 740,742, 744 with respect to the proximal branch portion struts 750, 752,754.

As shown in FIGS. 51-52, an alternative stent 812 and branch portion 830is shown. In this embodiment, branch portion 830 is similargeometrically to branch portion 330 described above; however, branchportion 830 has a modified strut structure comprising a nested strutconfiguration with distal branch portion 836 nested within proximalbranch portion 832. In particular, in the unextended position, distalbranch struts 840, 842, 844 are in phase with and nested within proximalstruts 850, 852, 854 of branch portion 830. Longitudinal strut portions845 and the respective curved portions 847 of distal branch portionstruts 840, 842, 844 are positioned within longitudinal strut portions855 and the respective curved portions 857 of respective proximal branchportion struts 850, 852, 854. The outside lateral distal struts 840, 844are connected to the outside lateral proximal struts 850, 854 at curvedregions 860, 862, thus defining a single bounded space or opening 863between the distal branch portion struts 840, 842, 844 and the proximalbranch portion struts 850, 852, 854. As best seen in FIG. 52, opening863 is smaller than the opening 364 of branch portion 330 describedabove. As described above with respect to other embodiments, inoperation, branch portion 830 is configured to extend outwardly withrespect to stent body 814. When branch portion 830 is fully extended itmay provide at least partial stent coverage of both the proximal anddistal side of the inner branch vessel wall. In particular, branchportion 830 may pivot at curved regions 864, 866, such that the branchportion 830 is in a first position extended outward from the remainderof stent body 814 and into the branch vessel to support a portion of thebranch vessel wall. Branch portion 830 may be further extended to asecond position by pivoting distal branch portion struts 840, 842, 844inward about curved regions 860, 862 and separating the distal branchportion struts 840, 842, 844 from the proximal branch portion struts850, 852, 854 to support the branch vessel opposite the proximal branchportion struts. It will be recognized that the exterior surface of theproximal branch portion struts 850, 852, 854 contact and support thebranch vessel wall and the undersurface of the distal branch portionstruts 840, 842, 844 contact and support the branch vessel wall in thesecond extended position. Stent 812 may be delivered in a similar manneras described above with respect to stent 312 and branch portion 830 maybe extended in a similar manner as branch portion 330. In particular,branch portion 830 be moved from the first extended position to thesecond extended position by applying force in the distal direction on asecond catheter extending through opening 863 to move and/or pivot thedistal portion struts 840, 842, 844 with respect to the proximal branchportion struts 850, 852, 854.

The stent can also be described as comprising a branch band 834 thatincludes the branch portion 830. The branch band 834 comprises anon-split portion wherein the struts and turns do not split, and a splitportion 830 wherein the struts comprise split struts and the turnscomprise split turns. In an unextended configuration, the split portion830 defines a serpentine gap within the branch band. The split gap isentirely bounded by said branch band 834, and is not bounded by anyconnectors 26 that extend between adjacent serpentine bands 28.

As shown in FIGS. 53-54, an alternative stent 912 and branch portion 930is shown. In this embodiment, branch portion 930 is similargeometrically to branch portion 830 described above; however, branchportion 930 has a modified strut structure wherein the outside lateraldistal branch struts 940, 944 are connected to the outside lateralproximal branch struts 950, 954 at curved regions 960, 962 adjacent theproximal end of outside lateral proximal struts 950, 954. In thisregard, in operation, branch portion 930 may pivot at curved regions960, 962, such that the branch portion 930 is in a first positionextended outward from the remainder of stent body 914 and into thebranch vessel to support a portion of the branch vessel wall. Branchportion 930 may be further extended to a second position by pivotingdistal branch portion struts 940, 942, 944 inward about curved regions960, 962 and pivoting the proximal curved regions 949, 951 of distalbranch portion struts 940, 942, 944 downward about the distal curvedportions 941 and 945. In this second extended position, distal branchportion struts 940, 942, 944 are spaced from the proximal branch portionstruts 950, 952, 954 to support the branch vessel wall opposite theproximal branch portion struts. It will be recognized that the exteriorsurface of the proximal branch portion struts 950, 952, 954 contact andsupport the branch vessel wall and the undersurface of the distal branchportion struts 940, 942, 944 contact and support the branch vessel wallin the second extended position. Stent 912 may be delivered in a similarmanner as described above with respect to stent 812 and branch portion930 may be extended in a similar manner as branch portion 830.

Referring to FIGS. 55-56, an alternative stent 1012 and branch portion1030 is shown. In this embodiment, branch portion 1030 is similargeometrically to branch portion 830 described above; however, distalbranch portion is attached to distally adjacent ring 1038 by a singleconnector 1070. Connector 1070 longitudinally connects at least one ofdistal branch struts 1040, 1042, 1044 to ring 1038. In this embodiment,connector 1070 connects ring 1038 to one of the proximal curved portions1049, 1051, 1053 of distal branch struts 1040, 1042, 1044. In operation,branch portion 1030 is extended in much the same manner as branchportion 830, except a portion of the distal branch portion adjacentconnector 1070 at least partially resists extension outward to the firstextended position and the distal branch portion may rotate outward withrespect to the junction or point at which connector 1070 meets thedistal branch struts. In the second extended position, connector 1070preferably contacts and supports a portion of the ostium or thetransition area of the vessel wall where the main vessel meets thebranch vessel.

The stents described herein may have one or more drugs coated thereon.An exemplary drug coating is described in WO 04/009771. One particularapplication for the use of a stent with a branch portion 30, 330, 430,530, 630, 630, 830, 930, 1030 described above is for localized drugdelivery.

One or more drug coatings may be present at any location in or on thewalls of stents according to the present invention, including in or onthe wall of the main vessel portion of the stents, or in or on the wallof the branch portion of stents. The position of depot(s) depends ondesired site(s) of highest concentration of drug delivery.

Thus, the length, width, and thickness of a depot are variables that canbe tailored according to the desired drug distribution and the size ofthe main and branch vessels to be treated. For example, a depot that isthick enough to impede fluid flow in a narrow vessel may be an optimalthickness for a larger vessel.

Stents according to the present invention can be used as vehicles forlocalized delivery of drugs to cells of the walls of both the main andbranch vessels at the location of the stent. Drugs that are particularlysuitable for treatment of cells in the immediate area of the stentinclude anti-restenosis and anti-thrombotic drugs. If desired, differentconcentrations of drugs, or different drugs, may be included in depot(s)located in or on different areas of the stent walls. For example, it maybe desirable to treat the cells of the main vessel with a first drug,combination of drugs, and/or concentration of drug(s) and to treat thecells of the branch vessel with a second, different, drug, combinationof drugs, and/or concentration of drug(s). As another example, it may bedesirable to maintain a high concentration of anti-restenosis drug(s)near the bifurcation of the vessels. As yet another non-limitingexample, it may be desirable to maintain a high concentration ofanti-restenosis drug(s) at the three open ends (two on the main portionand one on the branch portion) of the stent. It will be appreciated byone skilled in the art upon reading the present disclosure that manycombinations of two or more depots are possible within the spirit andscope of the present invention.

The present invention also provides kits comprising a stent or stentsaccording to the present invention. In addition to a stent or stents, akit according to the present invention may include, for example,delivery catheter(s), balloon(s), and/or instructions for use. In kitsaccording to the present invention, the stent(s) may be mounted in or ona balloon or catheter. Alternatively, the stent(s) may be separate fromthe balloon or catheter and may be mounted therein or thereon prior touse.

While the invention has been described in conjunction with specificembodiments and examples thereof, it is evident that many alternatives,modifications and variations will be apparent to those skilled in theart upon reading the present disclosure. Accordingly, it is intended toembrace all such alternatives, modifications and variations that fallwithin the spirit and broad scope of the appended claims.

1. A stent comprising: an expandable framework comprising a plurality ofserpentine bands including a branch band, adjacent serpentine bandsconnected by connector struts, said branch band consisting ofalternating struts and turns, said branch band comprising a firstportion and a second portion, said first portion comprising a pluralityof non-split struts and non-split turns, said second portion comprisinga plurality of split struts and split turns that define a serpentinegap, said serpentine gap bounded entirely by said branch band.
 2. Thestent of claim 1, wherein said branch band consists of said firstportion and said second portion, said first portion consisting ofnon-split struts and non-split turns, said second portion consisting ofsplit struts and split turns.
 3. A bifurcation stent having anunextended configuration and an extended configuration, the stentcomprising: a main stent body comprising a body wall, the body wallcomprising a plurality of adjacent serpentine bands, each serpentineband comprising a plurality of struts; said serpentine bands including abranch band consisting of alternating struts and turns, a portion ofsaid struts and turns comprising split struts and split turns, in theunextended configuration the split struts and split turns defining acell within the branch band having a serpentine shape, in the extendedconfiguration, the cell comprises a side branch opening.
 4. Thebifurcation stent of claim 3, wherein body wall further comprises aplurality of connectors, the connectors connecting adjacent serpentinebands to one another.
 5. The bifurcation stent of claim 4, wherein saidbranch band defines a proximal side and a distal side, said split turnscomprising proximal split turns located on said proximal side and distalsplit turns located on said distal side, wherein a plurality of proximalsplit turns are each connected to a connector and a plurality of distalsplit turns are not connected to a connector.
 6. The bifurcation stentof claim 5, wherein each proximal split turn is connected to a connectorand each distal split turn is not connected to a connector.
 7. Thebifurcation stent of claim 5, wherein the body wall includes aserpentine band located immediately proximal to the branch band, and theconnectors that connect to said proximal split turns also connect to theserpentine band located immediately proximal to the branch band.
 8. Thebifurcation stent of claim 3, wherein, in the unextended configuration,said cell is the only cell of the stent defined entirely by said branchband.
 9. The bifurcation stent of claim 3, wherein, in the unextendedconfiguration, said split struts and split turns comprise a firstcontinuous serpentine portion and a second continuous serpentineportion, said first and second continuous serpentine portions boundingthe cell having a serpentine shape.
 10. The bifurcation stent of claim9, wherein, in the unextended configuration, the first continuousserpentine portion extends substantially parallel to the secondcontinuous serpentine portion.
 11. The bifurcation stent of claim 3,wherein, in the unextended configuration, the branch band comprisesoutside lateral proximal struts and outside lateral distal struts, eachof the outside lateral proximal struts connected to an outside lateraldistal strut at a curved portion, said curved portions defining ends ofsaid cell having a serpentine shape.
 12. The bifurcation stent of claim11, wherein said split struts and split turns are disposed between thecurved portions.
 13. A bifurcation stent comprising: a main stent bodyhaving a body wall comprising a plurality of adjacent serpentine bands,a portion of the body wall comprising a branch band consisting ofalternating struts and turns, said branch band including a branchportion, the branch portion having an unextended configuration and anextended configuration; in the unextended configuration, the branchportion comprising a plurality of nested struts including first strutsand second struts, the first struts comprising longitudinal strutportions connected to one another at first curved portions, the secondstruts comprising longitudinal strut portions connected to one anotherat second curved portions, said first struts and second struts boundinga cell; in the extended configuration, the cell comprises a side branchopening.
 14. The bifurcation stent of claim 13, wherein, in an extendedconfiguration, the branch portion defines a branch lumen.
 15. Thebifurcation stent of claim 13, wherein at least one of the first curvedportions is nested within at least one of the second curved portions.16. The bifurcation stent of claim 13, wherein at least one of thesecond curved portions is nested within at least one of the first curvedportions.
 17. The bifurcation stent of claim 13 further comprising aplurality of connectors, at least one of the connectors connecting thebranch portion to the main stent body.
 18. The bifurcation stent ofclaim 17, wherein the main body wall includes a serpentine bandimmediately proximal to the branch portion and a serpentine bandimmediately distal to the branch portion, at least one of the firstcurved portions is connected to the serpentine the serpentine bandimmediately proximal to the branch portion by a connector.
 19. Thebifurcation stent of claim 18, wherein one of the second curved portionsis connected to the serpentine band immediately distal to the branchportion by a connector.
 20. The bifurcation stent of claim 19, whereinadjacent serpentine bands are connected one to another via a pluralityof said connectors.